The present invention relates to a resistance welding controller which supplies a given level of alternating ("AC") current to a resistance welder.
A resistance welder welds a workpiece sandwiched between two electrodes as current flows. The current flow heats the workpiece and forms a molten metal weld "nugget." After the welding current stops flowing, the weld nugget solidifies to form the weld.
There are two types of resistance welders: AC and direct ("DC") current. A DC resistance welder and an associated resistance welding controller provide the advantage that the current supplied to resistance welder (and, in turn, to the electrodes) can be controlled within stringent limits. However, there are two major disadvantages: the equipment required is expensive and the electrodes wear out quickly because current flows in one direction only during welding. In contrast, an AC resistance welder and an associated resistance welding controller provide the advantages that the equipment required is inexpensive and the electrodes wear out very slowly. However, a disadvantage is that current supplied to the AC resistance welder 80 (and, in turn, to the electrodes) can be controlled only within fairly loose limits.
One way to control both types of resistance welders is to install a separate resistance welding controller for each. However, having two separate controllers is costly.
In view of the foregoing, it would be desirable to provide a resistance welding controller which can control both AC and DC resistance welders while using electricity efficiently and improving welding performance.